Question

Apply your understanding of the various components of the electron transport chain to evaluate how the roles of ubiquinone and cytochrome c differ from those of the other components.

a) Ubiquinone transfers electrons between complexes, while cytochrome c is a proton pump
b) Cytochrome c transfers electrons between complexes, while ubiquinone is a proton pump
c) Ubiquinone and cytochrome c both transfer electrons between complexes
d) Ubiquinone and cytochrome c are not involved in the electron transport chain

Answer 1

Ubiquinone functions as a lipid-soluble mobile electron carrier transferring electrons from complexes I and II to III, while cytochrome c is a hydrophilic mobile electron carrier that transports electrons from complex III to complex IV. Both do not function as proton pumps.

Step-by-step explanation:

The roles of ubiquinone (also known as coenzyme Q) and cytochrome c in the electron transport chain are distinct from the roles of the complexes I, II, III, and IV. Unlike the membrane-bound complexes that pump protons and play a part in the creation of a proton gradient, ubiquinone and cytochrome c are mobile electron carriers. Ubiquinone moves within the lipid bilayer of the inner mitochondrial membrane, receiving electrons from complexes I and II, and transferring them to complex III. This molecule is lipid-soluble, which allows it to move freely within the hydrophobic core of the membrane. On the other hand, cytochrome c is a hydrophilic electron carrier that transports electrons from complex III to complex IV along the surface of the inner membrane facing the intermembrane space. Neither ubiquinone nor cytochrome c function as proton pumps.